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Conditional Statements#

Conditional statements are a fundamental component of the Miva Merchant Template Language, enabling developers to control the flow of logic in their templates. By using conditional statements, you can dynamically render content, implement decision-making logic, and create personalized user experiences based on various conditions.

This section covers the syntax and usage of the three primary conditional statements in Miva: <mvt:if>, <mvt:else>, and <mvt:elseif>.

<mvt:if>: Basic Conditional Logic#

The <mvt:if> tag is used to execute a block of code if a specified condition evaluates to true. If the condition is not met, the code inside the <mvt:if> block is skipped.

Syntax:#

<mvt:if expr="condition">
    <!-- Code to execute if the condition is true -->
</mvt:if>

Example: Checking the Current Screen#

<mvt:if expr="g.Screen EQ 'SFNT'">
    <p>Welcome to our storefront!</p>
</mvt:if>

In this example, the condition checks if the global variable g.Screen equals 'SFNT' (the storefront screen). If true, the message “Welcome to our storefront!” is displayed.

Key Components of a Condition:#

  1. Variable: The data being evaluated (e.g., g.Screen).
  2. Comparison Operator: Determines how values are compared (e.g., EQ, NE, GT).
  3. Value: The value being compared against (e.g., 'SFNT').

<mvt:else>: Providing an Alternative#

The <mvt:else> tag is used to execute code if the condition in the <mvt:if> block is not met. This allows you to handle alternative scenarios.

Syntax:#

<mvt:if expr="condition">
    <!-- Code to execute if the condition is true -->
<mvt:else>
    <!-- Code to execute if the condition is false -->
</mvt:if>

Example: Displaying Alternative Content#

<mvt:if expr="g.Screen EQ 'SFNT'">
    <p>Welcome to our storefront!</p>
<mvt:else>
    <p>Check out our latest deals on <a href="/products">products</a>!</p>
</mvt:if>

If g.Screen equals 'SFNT', the storefront message is displayed. Otherwise, the alternative message encouraging users to view products is shown.

<mvt:elseif>: Evaluating Multiple Conditions#

The <mvt:elseif> tag allows you to check additional conditions within the same conditional block. It eliminates the need to write separate <mvt:if> statements, streamlining your logic.

Syntax:#

<mvt:if expr="condition1">
    <!-- Code to execute if condition1 is true -->
<mvt:elseif expr="condition2">
    <!-- Code to execute if condition2 is true -->
<mvt:else>
    <!-- Code to execute if neither condition is true -->
</mvt:if>

Example: Handling Multiple Screens#

<mvt:if expr="g.Screen EQ 'SFNT'">
    <p>Welcome to our storefront!</p>
<mvt:elseif expr="g.Screen EQ 'PROD'">
    <p>Buy now and get free shipping on orders over $50!</p>
<mvt:else>
    <p>Explore our categories for the best deals!</p>
</mvt:if>

In this example:

  • If the screen is 'SFNT', a welcome message is displayed.
  • If the screen is 'PROD', a promotion message is displayed.
  • If neither condition is met, a general call-to-action message is shown.

Best Practices for Conditional Statements#

  1. Simplify Logic:

    • Avoid overly complex expressions in a single <mvt:if> or <mvt:elseif> statement.
    • Break down large conditions into smaller, readable parts.

  2. Use Logical Operators:

    • Combine conditions using AND or OR to handle multiple scenarios in one statement.
    • Example: 
      <mvt:if expr="g.Screen EQ 'SFNT' AND g.User_Type EQ 'admin'">
    <p>Welcome, Admin, to the storefront!</p>
</mvt:if>

  3. Provide Defaults:

    • Always include an <mvt:else> block to handle unexpected scenarios or provide fallback content.

  4. Comment Your Code:

    • Document complex conditions to make your logic easier to understand and maintain.

Advanced Example: Nested Conditions#

For more complex scenarios, you can nest conditional statements to evaluate multiple layers of logic.

<mvt:if expr="g.User_Logged_In EQ 'yes'">
    <mvt:if expr="g.Screen EQ 'SFNT'">
        <p>Welcome back to our storefront!</p>
    <mvt:else>
        <p>Enjoy exploring our site!</p>
    </mvt:if>
<mvt:else>
    <p>Please <a href="/login">log in</a> to see personalized content.</p>
</mvt:if>

In this example:

  • If the user is logged in and on the storefront screen, a personalized message is displayed.
  • If logged in but not on the storefront screen, a general message is shown.
  • If not logged in, the user is prompted to log in.

Summary#

Conditional statements like <mvt:if>, <mvt:else>, and <mvt:elseif> are powerful tools for building dynamic and engaging Miva Merchant templates. By mastering these tags and adhering to best practices, you can create flexible templates that adapt to a wide range of scenarios.